A variety of closures have been proposed over the years for use with containers wherein the closure has a snap-action hinge for biasing the cover or lid to an open position on one side of an over center point and to a closed position on the other side of the over center point.
Some snap-action closure designs provide a one-piece unitary structure. While snap-action closures that have been used or proposed in the past may generally function well in the applications for which they were designed, it would be desirable to provide an improved one-piece unitary closure having a special inoperative orientation to accommodate molding and/or cleaning of the closure.
Further, it would be advantageous if such an improved closure could be provided wit a structure for permitting the closure to be fabricated with a generally smooth, planar top for certain applications where such a configuration would be desirable.
U.S. Pat. No. 4,124,151 discloses a low friction conical trunnion and bearing design in a snapaction closure having a spring-biased lid. The patent states that the closure lid spring structure is not held under any significant compression or tension when the lid is in either the open position or the closed position and, as a consequence, the structure will not take a "permanent set" as a result of being subjected to a pressure or force throughout a prolonged period. While such a closure design may result in lower stresses, it would be beneficial to provide a snapaction closure with an improved structural configuration that could accommodate manufacturing or molding tolerances so as to generally insure that the structure, if fabricated within those tolerances, would not be subjected to significant stresses in either the fully opened or fully closed positions of the lid.